An RF transmitter/receiver (transceiver) may be electrically coupled to an antenna to transmit and receive electromagnetic radiation. The electrical coupling can be designed to create a conjugate impedance match between the transceiver and the antenna, which maximizes the power transfer between the transceiver and the antenna. In a controlled environment, the antenna input impedance remains constant, so a fixed electrical coupling generally maintains the conjugate match. In real-world environments, however, antenna detuning may occur when the input impedance of the antenna is perturbed by various factors (e.g., objects near the antenna or agents such as ice forming directly on the antenna structure).
Small RF transceivers, with correspondingly small antennas, are especially susceptible to performance degradation if the impedance of the antenna is perturbed. Antenna detuning reduces the power available to the receiver and the transmit power radiated, but it can also severely degrade the efficiency of the power amplifier in the transmitter portion of the transceiver. A conventional solution is to add a tunable impedance matching network before the antenna, along with a tuning detection network, both of which add significant losses.